The invention relates to an optoelectronic component with a light emitting or light receiving element and a system carrier supporting said element for the support or installation of said component, an auxiliary carrier transparent to light in at least some areas or at least translucent and made of heat conducting material being provided, said auxiliary carrier being connected to the system carrier and thermally coupled to the element and having a recess through which light passes, together with a method for manufacturing such an optoelectronic component.
Light emitting or receiving optoelectronic components are becoming increasingly important with a view to providing fast and reliable data transmission media. In such components an optical coupling of the active element, usually made of semiconductor materials, to the environment or to an optical fibre is necessary. This places increased requirements on the housings which enclose the semiconductor elements, which must ensure adequate stability for use of the components under usual conditions.
Technologies used up to now for constructing surface emitting or receiving optoelectronic components such as light emitting diodes (LEDs) as incoherent light sources, or in particular surface emitting laser diodes, so-called VCSELs (Vertical Cavity Surface Emitting Lasers) as coherent light sources, have been manufactured up to now in metal housings of relatively large dimensions (in relation to the desired degree of miniaturisation) (TO housings) with transparent windows, and usually with very complex and therefore expensive manufacturing techniques. Also known are less expensive structures with completely moulded transparent housings of plastics material (for example, the customary LED housing) or pre-moulded plastic housings with moulded-in transparent plastic portions. The disadvantage of these constructions, in particular of the cheap construction of the LED plastic moulding-in technique which finds billions of applications, lies in the fact, in particular in the case of VCSEL diodes, that when manufactured with transparent plastics materials these components cannot be produced with sufficient optical quality and/or mechanical precision for coupling to an optical fibre. For this reason only the expensive TO housings with inset optical window cap have been used up to now.
A further difficulty with regard to the required miniaturisation results from the necessity when operating some optoelectronic components to incorporate a sensor or detector monitoring the operation or adjustment of the component in the housing of the optoelectronic component. According to the prior art, as shown in EP 0 786 836 A2, this is effected by the complex installation e.g. of monitor diodes in the TO housing used. This construction is very complex with regard both to the housing materials used and to the manufacturing steps, and thus is cost-intensive. However, for manufacturing reasons, the less expensive construction by the plastic moulding-in technique permits only limited incorporation of additional monitoring functions by additional elements. A further major disadvantage of the plastic moulding-in technique is that, when used with fibre optics, the stability of the structures and materials used for the plastic housing body is insufficient for precise coupling of the connected fibres. Plastic housing bodies can therefore be used for secure coupling only up to a maximum glass fibre diameter of 50 xcexcm, and in particular cannot be used for single-mode fibres.
A further problem with optically emitting components is power loss in light generation. The heat arising in such components reduces the optical conductivity, sometimes substantially, by heating up the active light emitting zones.
Known from DE 195 27 026 A1 is an optoelectronic component which has a radiation emitting and/or receiving semiconductor element as the light emitting or receiving element. The semiconductor element is fixed to a carrier plate which rests on a base plate with an opening. The radiation emitted from the semiconductor element can pass out through the carrier platet and the opening in the base plate. To focus the radiation emitted by the semiconductor element the carrier plate has a lens configuration in the area of the opening in the base plate.
Known from Patent Abstracts of Japan, E-1290, 1992, Vol. 16/No. 542, JP 4-207079 A is a layer construction on a substrate in which a photodiode is formed to detect the light emitted to the layer construction.
Further known from U.S. Pat. No. 4,967,241 is a layer construction on a substrate in which a funnel-shaped passage is formed for the light emitted by the layer construction. A photodiode is formed in the substrate to detect the light emitted from the layer construction.
Finally, Patent Abstracts of Japan, E-712, 1989, Vol. 13/No. 51, JP 63-244781 A discloses a tubular housing with a funnel-shaped opening behind which a light emitting element is mounted. The light emitted by the light emitting element is focused by a spherical lens arranged in the funnel-shaped opening.
It is the object of the invention to make available an optoelectronic component which can be manufactured at low cost and with the necessary optical qualities, and which reduces the heat generated in the element through energy dissipation and ensures good optical imaging or coupling out of the light.
This object is achieved with regard to the device and with regard to the method according to the claimed invention.
According to the invention an auxiliary carrier which is transparent at least in some areas or is at least translucent and is made of heat conductive material is provided, and firstly is connected to the system carrier and secondly is thermally coupled to the element. The feature xe2x80x9ctransparent in some areas or at least translucentxe2x80x9d means that either the material of the auxiliary carrier itself is transparent or an opening or at least a recess allowing the passage of light is provided.
The invention further proposes to provide an auxiliary carrier for the light emitting or receiving element, which carrier ensures optimal thermal conduction in particular to the system carrierxe2x80x94while being of very small dimensionsxe2x80x94and at the same time does not obstruct the inward or outward passage of light or ensures a targeted emission of light. A further advantage resulting from this feature is that the mounting of the element connected to the auxiliary carrier on the system carrier is substantially simplified since the dimensions of the system carrier are larger than those of the element alone and the auxiliary carrier is less sensitive when manipulated.
Following the principle of the invention a recess through which light passes is provided in the auxiliary carrier. Through said recess light rays for which the material of the auxiliary carrier is insufficiently transparent or is completely non-translucent can also penetrate the auxiliary carrier. To this end the recess is covered by a thin, light-permeable covering layer formed from said auxiliary carrier. The thickness of the light-absorbent material through which the light must pass is thereby reduced to a minimum. It is possible to form a sensor through which light is to pass in the relatively thin covering layer.
According to a preferred embodiment of the invention the auxiliary carrier is mechanically connected to the element in a planar fashion. Good heat dissipation from the element into the auxiliary carrier and a secure connection are thereby ensured. The auxiliary carrier is advantageously connected electrically to the element by means of an electrical bonding, facilitating current supply and signal conductance.
According to a further advantageous and therefore preferred embodiment of the invention a light-sensitive sensor is formed on or in the auxiliary carrier. Likewise, according to another advantageous embodiment of the invention a light-sensitive sensor is formed on or in the element. The advantage of this arrangement is that a sensor no longer needs to be installed in the housing incorporating the element by means of complex assembly steps. The direct integration in the auxiliary carrier makes it possible during irradiation of same to detect, for example, the quality or quantity of the emitted or received light independently of the element. Through such forming of a sensor in the auxiliary carrier or in the element itself complex and costly manufacturing steps can be saved and the efficiency of production can be improved.
According to a further aspect of the invention the system carrier is provided with an opening which allows light to pass through said system carrier. According to these embodiments the recess in the auxiliary carrier and/or the opening in the system carrier advantageously has the form of a truncated cone or truncated pyramid or is cylindrical with smooth side faces. By this means a divergent beam can emerge unobstructed and an incident beam can be concentrated by suitable measures into the area through which light passes.
According to a further preferred embodiment of the invention a focusing arrangement and/or an arrangement which changes the beam path of the light is advantageously arranged in the optical axis of the component. The quality and form of the beam and the coupling in and out of the light can thereby be advantageously influenced. Accordingly, in one embodiment of the invention the optical arrangement is advantageously fitted inside the opening of the system carrier and/or the recess of the auxiliary carrier.
According to a further advantageous aspect of the invention the optical arrangement is formed as a lens or a transparent platelet which is arranged between the surface normal of said platelet and the optical axis of the component at a defined angle which, according to another advantageous embodiment of the invention, is so selected that the smallest possible proportion of the emitted light is reflected by the surface of the platelet, and/or that a predetermined proportion is reflected in a defined direction. Through the reflection of a proportion of the emitted light, said proportion can be coupled into the sensor for evaluation.
An adhesive or bonding agent by means of which the optical arrangement is fixed inside the opening of the system carrier is preferably provided. A secure fixing of the optical arrangement is thereby achieved.
Advantageously, predetermined support points or support edges are provided on the side faces and/or edges of the recess of the auxiliary carrier and/or the side faces and/or edges of the opening in the system carrier for the self-adjusting alignment of the optical arrangement with respect to the optical axis of the component. A complex and error-prone positioning of the optical arrangement with respect to the element is thereby eliminated. Rapid and low-cost positioning of the optical arrangement is therefore possible. Consequently the support points or support edges are advantageously arranged on the outermost edges of the recess facing away from the element and/or on the outermost edges of the opening facing away from the element and/or on a middle section of the wall of the opening or recess.
According to a further preferred aspect of the invention the sensor is formed by an active electronic component, in particular a semiconductor component structured in or on the auxiliary carrier or its covering layer or in or on the element, the auxiliary carrier consisting preferably of a silicon substrate or a silicon-carbon compound and, according to another further development, the sensor is electrically coupled to the element indirectly via another circuit or directly. This makes possible a particularly reliable and inexpensive integration of the sensor, which is advantageously formed by a diode or a transistor, into the auxiliary carrier or into the element.
According to an especially preferred embodiment of the invention the element is formed by a VCSEL chip (coherently radiating diodes), an IRED chip (IRED=InfraRed Emitting Diode), spontaneously emitting diodes, or another chip emitting light on one surface. The resulting heat generated by energy dissipation is quickly dissipated through the good thermal conductivity of the auxiliary carrier to the system carrier connected thereto, so that reliable operation unrestricted by heat build-up is possible. The light emitting lateral face faces towards the auxiliary carrier which is irradiated by the light.
According to a further embodiment of the invention the system carrier is at least partially encapsulated with the auxiliary carrier fixed to it, by a non-transparent pressing, casting or moulding mass. Safe handling and reliable operation of the optoelectronic component are thereby ensured and miniaturisation of the housing, for example to SMD dimensions, is made possible.
The method for producing an optoelectronic component according to the invention, said component consisting of an element emitting or receiving light on a light transmitting surface and a system carrier supporting said element, provides for the connection of an auxiliary carrier transparent in at least some areas or at least translucent and made of thermoconductive material to the element, a thermal coupling between the auxiliary carrier and the element being produced. According to this method a mechanical connection of the auxiliary carrier supporting the element to the system carrier is provided.
A recess for the unimpeded passage of light through the auxiliary carrier is formed according to a process step according to the invention by anisotropic etching before connection of the auxiliary carrier to the element. Then, in a further process step while etching the recess, a covering layer with a thickness of  less than =50 xcexcm and covering the recess is left in place. The formation of a light-permeable sensor even when an absorbent material is used for the auxiliary carrier is thereby made possible.
According to a further especially preferred process step the formation of a sensor independent of the element is provided on or in the auxiliary carrier and/or the element by means of structuring steps used in semiconductor technology, before connection of these parts.
According to a further advantageous process step a multiplicity of auxiliary carriers, to be separated in a further process step, is combined jointly in a composite structure with independent sensors and/or the elements to be connected to same.
Also preferred is the fixing of an optical arrangement in the opening of the system carrier, the optical arrangement being advantageously bonded into the opening by means of an adhesive or bonding agent.
The system carrier is advantageously encapsulated at least partially with the auxiliary carrier attached to it and the element located on it, by means of a non-transparent pressing, casting or moulding mass.
Further advantages, peculiarities and advantageous further developments of the invention emerge from the subsidiary claims.